This invention relates to a flash (or arc) lamp comprising an insulative envelope containing a gas and housing a pair of arcing electrodes; and to a corresponding method of manufacturing such a flash lamp and apparatus for the same.
As is known, the ignition/triggering properties of arc and flash lamps are notoriously inconsistent from one batch of lamps to another and from one lamp to another.
The triggering process is complex and requires an initial breakdown or ionization in the lamp gas (e.g., xenon and krypton). Most triggering schemes use a trigger transformer to produce the high voltage required to achieve the ionization. Such ionization can typically be seen as a thin streamer between the two electrodes and forms the conductive path which allows a main energy storage capacitor to discharge across the electrodes, thus leading to an intense flash.
To improve the triggering process, it is known to sputter part of the electrode material on to the inner surface of the envelope near to the electrode. As a consequence, the voltage required to ignite a lamp can be significantly lowered.
However, such sputtering can be disadvantageous in that there can be a reduction in lifetime due to the sputtered material blocking light transmission from the plasma (leading to subsequent deglazing or recrystallization of the envelope material). Also, the sputtering process can damage the electrode surface and reduce the life of the lamp as the lamp plasma itself is used for the sputtering. Furthermore, the sputtering process needs to be carried out during or prior to the gas filling of the lamp, which is normally a lengthy and unpredictable process. For example, it can be achieved by reverse polarity running the lamp at a low gas pressure.